Type III Secretion Systems: Bacterial Injection Devices for Microbe-Host Interactions.

Many pathogenic and symbiotic bacteria interact with their eukaryotic host using a complex protein secretion apparatus termed the type III secretion system. Type III secretion systems are multiprotein machineries that form a complex syringe-like organelle spanning the entire Gram-negative bacterial envelope. The bacteria use these machineries to translocate effector proteins into the host cells that either enable them to evade the host's immune system or help establish a close relationship that is necessary to engage in a mutualistic symbiosis. This work discusses the occurrence, structure, and regulation of these novel and important protein translocation systems. [ABSTRACT FROM AUTHOR]